The popularity of both cordless telephones and cellular telephones has grown dramatically over the last decade. Cordless telephones are typically used in a home to allow a user to place and receive telephone calls at virtually any point throughout the house, or even into the yard. Such a cordless telephone system typically includes a portable cordless handset and a single cordless base station that is connected to the public switched telephone network (PSTN) by telephone land lines. An advantage to these cordless telephone systems is that they operate over the existing telephone land lines interconnecting the building or house where the cordless base station is located and the central office of the local exchange carrier, and thus, are billed as simple telephone lines in accordance with the customary land-line prices of the local exchange carrier. However, these cordless telephone systems operate with relatively low power, and therefore, have a limited coverage range.
Cellular telephones, on the other hand, operate over very large coverage areas that are divided into cells. Each cell is serviced by a cellular base station that is connected to the PSTN via a mobile switching center (MSC), as well known in the industry. Thus, the cellular customer is able to maintain a communication link as the customer travels from cell to cell without interruption using hand-off techniques. This provides an extreme amount of flexibility to the cellular customer, not to mention that the cellular customer can operate their cellular telephone over virtually any of the cellular networks maintained by cellular service providers. Presently, a substantially large portion of the United States is serviced by at least one cellular network, including essentially all metropolitan areas and most interstate highways. However, the cost of using the cellular telephone service is generally greater than that of the cordless telephone service. Most cellular service providers charge their customers a flat monthly rate plus an additional surcharge based on customer's usage.
As a solution, cellular cordless telephones have been developed which combine the portability and large coverage areas of a cellular telephone system with the convenience and low cost of a cordless telephone system in a single handset referred to hereafter as a cellular cordless telephone.
In essence, a cellular cordless telephone has two or more modes of operation. In a first mode, referred to herein as the ricrocellular mode, the cellular cordless telephone operates in conjunction with a microcell base station that is connected directly to the central office of a local exchange carrier. Thus, the microcellular mode can include a variety of different type telecommunication services that may be combined with cellular phone service in a single telephone handset other than a cordless telephone, such as a is personal communication system (PCS). Generally, the microcellular mode is characterized by a relatively small coverage area serviced by a microcell base station that is connected to the central office of the local exchange carrier, i.e., the PSTN, via an intermediate two-wire connection. This two wire connection may, for instance, connect the microcell base station directly to the central office or it may connect the microcell base station to a wireless switch or corporate private branch exchange (PBX) within a building which is subsequently connected to the PSTN.
In the second mode, referred to herein as the cellular mode, the cordless cellular telephone operates in conjunction with cellular base stations that are connected to a mobile switching center (MSC) that is connected to the PSTN. Accordingly, the cordless cellular telephone in this mode operates as a traditional cellular telephone.
In operation, the cellular cordless telephone initializes in the microcellular mode to determine if it is within range of the microcell base station in order to take advantage of the lower cost land-line services such as cordless or PCS. If the cellular cordless telephone is not within range of the microcell base station, it switches to cellular mode, wherein it registers with the local cellular service provider as a cellular telephone. The cellular cordless telephone may also be provided with manual controls enabling the user to override the microcellular mode so as to operate the phone in a cellular mode from initialization. An example of a cellular cordless telephone can be found in U.S. Pat. No. 5,442,680 to Schellinger, et al., the disclosure of which is incorporated herein by reference.
With the popularity and use of cellular cordless telephones coming of age, it has been determined that the cellular telephone user who now uses a cellular cordless telephone in order to reduce cost will not receive the reliability and speed in data communications when operating in the microcellular mode. Particularly, the user of cellular cordless telephone services are more and more combining the functionality of portable data terminal equipment (DTE), e.g., the laptop computer or personal digital system, with cellular data communication equipment (DCE), e.g., a modem coupled to a cellular cordless telephone, in order to service their professional and personal needs. However, when a cellular cordless telephone is connected to a modem associated with a computer for establishing a data communication link with a remotely located modem associated with another computer, the user is unable to obtain the same speed and reliability when operating the cellular cordless telephone in the microcellular mode as opposed to connecting the modem directly to a wall jack provided by the local exchange carrier as a part of the land-line network. In today's extremely competitive market place, the inability to provide users with data communications with the speed and reliability that they are accustomed dramatically reduces a products desirability. Currently, no modem known to the present inventor is able to adequately address the poor performance found when using a cellular cordless telephone in the microcellular mode.
Thus, a heretofore unaddressed need exists in the industry for enabling faster and more reliable data communications using a cellular cordless telephone operating in a microcellular mode.